Simple, but good
You kept things very simple, which I thought to be quite good. It was an easy premise, and you managed to pull it off rather well.
The only thing I would recommend adding would be to add some music, or sound effects to the game. Even improving the graphics wouldn't hurt a but.
As far as the graphics in general, they were fine. It was basic, but all the bits of animation that you used were quite smooth. You might want to work on your collision detection a bit more, but you definitely seem to be on the right track.
Very decent quality for your first submission.